In Shanksville, Pa., Flight 93 Remembered

On Sept. 11, 2001, United Airlines Flight 93 crashed into an abandoned strip mine. The flight, which carried 44 people, including four hijackers, was heralded for the actions of passengers who apparently attempted to overpower the terrorists. Audie Cornish talks to NPR's John Ydstie about Sunday's events in Shanksville, Pa., where a moment of silence will mark the crash.